The present invention relates to a disk storage medium on which data is recorded by light (which will be referred to as an xe2x80x9coptical diskxe2x80x9d).
In recent years, optical disks such as DVD-RAM and DVD-RW have been used as storage media for recording digital information thereon at a high density. Each of these optical disks used commonly today is designed in such a manner as to record data of 4.7 GB per side by being irradiated with a laser beam having a wavelength of 650 nm through an optical system (e.g., objective lens) having a numerical aperture of 0.6. Thus, approximately one hour of video signal can be recorded on each side.
However, the maximum recordable length of approximately one hour is not long enough to cope with most of actual applications. Accordingly, to make those optical disks as handy as home video tape recorders, those optical disks should acquire an even greater storage capacity. Also, to perform editing and other types of operations by making full use of the random-access capability, which is one of advantageous features of the optical disks, video signal needs to be recorded for about five hours or more. In that case, the data storage capacity of the optical disks should be at least 23 GB and preferably more.
However, it is not easy to produce an optical disk with such a huge capacity because the recording density must be tremendously increased from the currently available one.
The present invention overcomes the problems described above, and a primary object thereof is to provide an optical disk that achieves a high recording density and a huge storage capacity.
An optical disk according to the present invention includes a land and a groove. On the optical disk, data is recorded on both the land and the groove. A distance between the center of the land and the center of the groove adjacent to the land is 0.28 xcexcm or more. And the optical disk has a data efficiency of 80% or more.
In one preferred embodiment, the data is recorded by using a modulation code of a 3T system.
In another preferred embodiment, the data is recorded by using a modulation code of a 2T system.
In another preferred embodiment, a product code is used as an error correction code.
In another preferred embodiment, the groove is wobbled.
In another preferred embodiment, the optical disk further includes a light transmitting layer on the surface of the disk on which the groove and the land have been formed. The light transmitting layer has a thickness of 0.2 mm or less.
Another optical disk according to the present invention includes a land and a groove. On the optical disk, data is recorded on either the land or the groove. A pitch of the groove and a pitch of the land are 0.32 xcexcm or more. And the optical disk has a data efficiency of 80% or more.
In one preferred embodiment, the data is recorded by using a modulation code of a 3T system.
In another preferred embodiment, the data is recorded by using a modulation code of a 2T system.
In another preferred embodiment, a product code is used as an error correction code.
In another preferred embodiment, the groove is wobbled.
In another preferred embodiment, the groove includes a plurality of wobble patterns.
In another preferred embodiment, the wobble patterns represent address information.
In another preferred embodiment, the optical disk further includes a light transmitting layer on the surface of the disk on which the groove and the land have been formed. The light transmitting layer has a thickness of 0.2 mm or less.
In another preferred embodiment, the optical disk has a storage capacity of 23 GB or more.
In another preferred embodiment, the optical disk further includes a recording layer of a phase change material and the data is rewritable.